I generally like the Lee molds but I have had problems with the aluminum galling from the action of the sprue cutting plate

One good trick with aluminum molds is to coat the top of the mold under the sprue plate with graphite. I use a carpenter's pencil, move the sprue plate out of the way, and scribble all over the top of the block. That graphite stays put on top of the block and seems to help the sprue plate glide without galling.